Tube shield



Dec. 2, 1958 E. P. REARDQN TUBE SHIELD Filed Dec. l0, 1954 EDWARD P. REARDON FIG. 5

HIS ATTORNEY.

United States Patent O fb TUBE SHIELD Edward P. Reardon, Oak Park, lll., assignor to Zenith Radio Corporation, a corporation of Delaware Application December 10, 1954, Serial N o. 474,485

2 Claims. (Cl. 174-35) This invention relates to shielding arrangements for use with electron-discharge devices.

In many types of radio and television apparatus, it is advantageous and even in some cases essential to provide electrical shielding for one or more of the electrondischarge devices. To this end many types of shields have been contrived, most of which utilize a surrounding metallic element which is clamped either to the tube itself or to the chassis on which the tube is mounted. For electrical shielding purposes, the shield may take any desired form so long as it is construed of conductive material, completely surrounds the tube, and is maintained in good electrical contact with the chassis. There are many applications in which, in addition to the requirement for electrical shielding, it is necessary or desirable to provide effective heat dissipation. Some forms of shields tend to concentrate heat generated in the normal operation of the tube, and unless this heat is dissipated in an efficient manner, overheating and ultimate failure of the tube may be encountered. In addition, and particularly in high-frequency applications such as television tuners and the like, it has been found that a considerable amount of extraneous noise is introduced whenever the tubes are permitted to overheat.

kIt is therefore a principal object of the present invention to provide a new and improved tube shield which overcomes one or more of the disadvantages of prior art devices.

It is a further object of the invention to provide a novel tube which in addition to providing efficient electrical shielding insures rapid dissipation of heat generated by the tube during normal operation of the associated apparatus.

Still another object of the invention is to provide a novel shield assembly including a tube shield and a cooperating saddle for use in preventing overheating of an associated electron-discharge device, while at the same time providing full electrical shielding.

A shield assembly constructed in accordance with the present invention and arranged for use with an electron-discharge device having a cylindrical envelope of a predetermined nominal diameter comprises a metal saddle and a cylindrical resilient sheet metal shield. The saddle is adapted to encompass the base of the tube and is provided with a plurality of bearing regions arranged in a generally cylindrical locus, as for example by forming the saddle as a simple cylindrical member or of sectionalized or mutilated-cylindrical construction in which portions of the cylinder are omitted and/o1 distorted. The shield member is formed of resilient sheet metal and is preferably provided with tightly overlapping paraxial edges, having a diameter normally less than the nominal diameter of the tube with which it is to be used but expandable on insertion of the tube so that the shield is maintained in intimate physical contact -With the envelope of the tube. The outermost one of the overlapping edges is rolled in to contact the body of the shield member throughout substantially 2,862,991 Patented Dec. 2, 1958 its entire axial length. The shield further comprises a plurality of integral spring lingers at one end, and these spring ngers are adapted to engage the bearing regions of the saddle to provide extended-area electrical and thermal contact between the shield and the saddle.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The organization and manner of operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing, in which:

Figure l is a fragmentary perspective view of a portion of a radio receiver or the like comprising an electron-discharge device provided with a shield assembly constructed in accordance with the present invention;

Figure 2 is a cross-sectional view of the shield member of the invention taken along a line similar to line 2-2 of Figure l prior to insertion of the associated electrondischarge device; and

Figure 3 is a detailed fragmentary view, partly in cross section, showing the manner in which Contact is made between the components of the shield assembly of Figure 1.

As shown in Figure l, the shield assembly of the present invention may comprise a resilient sheet metal shield member 10 and a generally cylindrical saddle 11 adapted for use with an electron-discharge device 12 mounted on the chassis 13 of a radio receiver or the like. The shield member 10 is of generally cylindrical configuration and is provided with tightly overlapping paraxial edges 14 and 15 with its natural resiliency being such as to maintain its diameter normally less than the nominal diameter of the envelope of the electron-discharge device 12 with which it is to be employed. Upon slipping shield '10 over tube 12 or inserting 12 in shield 10, the shield expands and is therefore maintained in intimate physical contact with the envelope of device 12. Shield 10 is also provided with a plurality of integral spring fingers 16 at one end. Each of the spring lingers is preferably formed by conventional punching and stamping operations, and these fingers are formed with an outwardly convex curvature in the manner shown to provide an outwardly biased spring contact with the inner surface of saddle 11. Shieldltl is also provided with an integral laterally extending loop 17 adapted to engage a guide rail 1S fixed to chassis 13 for the purpose of captivating the tube shield and thereby prevent accidental short circuiting of components, in the manner described in the copending application of George W. Long, Serial No. 474,480, led concurrently herewith, now Patent No. 2,851,513, issued September 9, 1958, and assigned to the present assignee.

As shown, saddle 11 is formed as a simple cylindrical metal number encompassing the base of tube 12 and provided with lateral flanges 19 to facilitate mounting to the chassis. However, other constructions for saddle 11 may also be employed if desired; for example a sectionalizedor mutilated-cylindrical saddle containing two or more cylindrical segments or distorted to conform to the curvature of spring fingers 16 may be employed. In any construction according to the invention, however, the saddle is provided with a plurality of bearing regions disposed in a generally cylindrical locus against which the spring fingers 16 of shield 1t) are biased upon insertion of the shield into the saddle.

When shield member 10 is slipped over the envelope of tube 12 and pressed downwardly to cause engagement of spring ngers 16 with the inner surface of saddle 11, complete electrical shielding is realized since tube 12 is completely surrounded with material of high conductivity. Spring lingers 16, being biased into rm engagement with 3 conductive saddle 11 in the manner shown in Figure 3, provide adequate grounding of the shield to the chassis. In addition, spring fingers 16 maintain excellent thermal contact with saddle 11, and since shield 10.is maintained.

in intimate engagement' or contact' with the envelope' of tube 12, heat generated by the tube during operation: of the equipment is normally transferredl by conduction to the shield and thence through spring fingers 16 to saddle 11 and' chassis 13 to assure rapid and eiiicient heat dissipation.

For best results, the outermost edge 14. of shield l@ is rolled inwardly as most clearly indicated in Figure 2 so that insertion oftube 12forces the innermost overlapping edge 15 outwardly into rm engagement with edge 14 along its fulllength. This arrangement prevents substantial leakage or inadequacy ofA electrical shielding which might otherwise be encountered. From a comparison of Figures 1 and 2, the manner in which insertion of the tube in shield member causes expansion of the latter may also be readily understood.

The shield and saddle of the present invention may be simply constructed by normal manufacturing techniques from inexpensive materials. Although certain of the constructional features are known in the prior art, it has been determined that the shield of the present invention is fully as effective from an electrical point of view as any previously known shields while providing materially improved heat dissipation. In particular, the shield of the invention has been tested in connection with an oscillator tube of a television tuner and in this environment has been found to prevent any substantial local oscillator radiation. At the same time, the use of the shield shown in Figure l has resulted in a reduction of operating temperature of the oscillator tube from as high as 190 C. with certain types of prior art shields to a more reasonable temperature of the order of 125 C. to 140 C. In addition to providing materially increased oscillator tube life, this reduction in operating temperature effects a marked improvement in the signal-to-noise characteristic of the television tuner.

While the shield member of the present invention is most effectively employed in conjunction with a cooperating saddle, it may also be employed in some instances to achieve beneficial results without the use of such a saddle.

While a particular embodiment of the present invention has been shown and described, it is apparent that changes and modifications may be made without departing from the invention in its broader aspects, and, therefore, the

aim in the appended claims is to cover all such changes and modiiications as fallk within the true spirit and scope` of the invention.

I claim:

l. A shield assembly for use with an electron-discharge device having a cylindrical envelope of a predetermined nominal diameter comprising: a metal saddle adapted to encompass the base of said device and provided with a plurality of bearing regions disposed in a cylindrical locus; and a cylindrical resilient sheet metal shield havingv tightly overlapping paraxial edges and a diameter normally less than said predetermined nominal diameter but expandable upon insertion of said device whereby said shield is maintained in intimate physical contact with said envelope, the outermost of'said overlapping edges being rolled in to Contact the body of said shield throughout substantially its entire axial length and said shield cornprising a plurality of integral spring ngers at one end thereof adapted to engage said bearing regions upon insertion of said shield in said saddle for providing extendedarea electrical and thermal co-ntact between said shield and said saddle.

2. A tube shield for use with an electron-discharge device having a cylindrical envelope of a predetermined nominal diameter and with a metal saddle encompassingy the base of said device, said shield comprising: a cylindrical resilient sheet metal member having tightly over'- lapping paraxial edges with a diameter normally less than said predetermined nominal diameter but expandableupon insertion of said device, whereby said member is maintained in intimate physical contact with said envelope, the youtermost of said overlapping edges being rolled in to contact the body of said shield throughout substantially` its entire axial length; and `a plurality of spring` lingers integrally formed in said cylindricalA member atl one end thereof and adapted to provide multipoint electrical and thermal contact with said metal saddle.

References Cited in the le of this patent UNITED STATES PATENTS 1,962,968 Nowosielski June 12, 1934 2,080,913y Hafecost et al. May 18, 1937 2,499,612 Staver Mar. 7, 1950 OTHER REFERENCES Miniature Tube Shield, advertisement in magazine Electronic Equipment of April 1954, page 42. (Copy in Div. 69.) 

